It sort of makes me a little angry that PR seems to forget that entire time frame as it never happened. I know it was a long time ago, but PR and CC worked together almost every day during the time they were paired. How can he forget so much about it?

I think it's like any project someone does at work. For example, someone could be a lawyer working intensively on a certain court case. As soon as that's over, he'll move on to a new case. If someone asks him the details of the first case even 5 years later (let alone 20), he's not going to remember that much, as he's currently working on something else.

We the fans (especially the fans here!) spend time watching YouTube, rehashing the old scenes and comparing them to current scenes, and/or reading fanfic, watching montages, etc. But the actors don't do this at all. They're immersed in their current stories, and I'd guess they almost never spend time as we do revisiting the old ones.